The present invention relates to improvements in papermaking machines, and more particularly to a method and device for separating the marginal edge of a paper web formed on a traveling wire wherein the web is single layer or multiple layered.
In a papermaking machine, the sheet or web is formed by depositing one or more layers of stock which is fibers in an aqueous suspension onto a traveling wire. The stock is normally derived from wood or other vegetable fibers, and the suspension of stock is delivered onto the traveling wire by headboxes having slice openings and positioned along the wire. The layers of stock which are formed in this manner have longitudinal edges which are not perfectly even or regular, both from the standpoint of their geometry and their dimension, and these edges must therefore be made even and regular after the headboxes have deposited the web on the wire. This is frequently done by means of devices which employ water jets which are directed onto the edges of the layers on the wire in order to separate the most irregular marginal portions from the web. The scrap which is generated by this separation arrangement is collected by ducts, and the material of the scrap is used for additional stock.
Methods and devices used heretofore for trimming or forming the edge of a traveling web have encountered disadvantages. First, they do not allow complete and useful recovery of the scrap material which is derived from the separated edge. This is because the usual edge forming device which is located a considerable distance downstream of the headbox separates the marginal portions of the single layer or the multi-layered web in a single operation, and when multiple layers are used, each of the layers normally comprises fibers of a different type and quality. That is, where multiple layer paper is made, one layer may be made of fibers that has unique tear strength, and another layer made of fibers has unique softness. If the edge from the multiple layers is separated, this mixes the fibers so that they cannot be used to make either layer. It is almost impossible to separate the fibers of the various layers after they have been intermixed and their subsequent use is considerably limited.
Accordingly, an object of the invention is to provide a method and a mechanism for adjusting and trimming the edge of one or more continuous layers of paper delivered by headboxes, and which enables the marginal portions of the edges of these layers to be separated while at the same time making it possible to completely reuse the fibers of the scrap stock separated from the edge of the web.
A further object of the invention is to provide a device for trimming the edge of a traveling paper web being formed which can be associated with the headbox and provides for separation at an early stage of the formation.
The concepts of the invention provide a method for adjusting the edge of one or more overlying layers of paper web deposited on an endless traveling wire of a papermaking machine wherein each of the layers is delivered through the slice opening of individual headboxes and where a blade separates the marginal portions of each edge of at least one of the layers from the remainder of the layers as it leaves the slice opening, and a stage is provided in which the scrap generated by separating the marginal portions is conveyed into a collector.
The invention also provides a device for adjusting the width or edge of at least one layer of a fibrous web deposited on a traveling wire of a papermaking machine wherein the layer is delivered through the slice of a headbox and the mechanism is characterized by a blade mounted on the headbox and positioned along the emerging stock jet with the blade located in a position to separate the marginal portion of at least one edge of one layer from the remainder of the layer and conveying means is provided by which the scrap generated by separating the edge is conveyed into a collector.
Other objects, advantages and features of the invention will become more apparent with the teaching of the concepts and principles of the invention in connection with the disclosure of the preferred embodiments thereof, in which: